Reliability of electronic components
A concern point for engineers is the failure rate figure of critical components. Such information is not always available in the part spec sheet. Thus, the designers turn to specialists to estimate this value and get an MTBF figure during the development stage before launching a new product.
Two failure conditions into components
1. Defective components are faulty from the moment they are born.
2. Faulty components are manufactured according to their rules and deteriorate over time or by exposure to high environmental stress.
Three factors may cause failures
(1) Hidden internal factors that settled in the piece from the birth;
(2) External stress caused by the environment, such as temperature and humidity;
(3) Physical degradation over time.
Periods of failures
To account for the failure periods of a component, a graph defined by a bathtub curve plots three correlation failure periods over time.
They are infant mortality, accidental failure, and wear-out period.
Infant mortality: The principal cause is hidden internal defects.
Failures occur suddenly after product startup and become progressively weaker over time.
Accidental failure: During this period, failures occur by accident at a constant rate and are not time-related, for example, lightning or electromagnetic forces.
Wear-out: At this point, the failure rate increases gradually over time. It is due to the wear of the product when it enters the end of life.
The failure analysis involves understanding the nature of product defects and investigating their location through electrical characteristics measurement and various observations.
This process encompasses a broad spectrum, including electronic parts like LSIs, resistors, capacitors, switches, connectors, PCBs, and contact points of electrical components. The MTTF analysis applies to these electronic pieces. The FIT (Failure In Time) is employed to express the value.
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